Sahih al-Bukhari 181
Sahih al-Bukhari · Book 4: Ablutions (Wudu') · (What is said regarding) a man who helps his companion to perform ablution (by pouring water for him)
Narrated Usama bin Zaid:
حَدَّثَنِي مُحَمَّدُ بْنُ سَلاَمٍ ، قَالَ أَخْبَرَنَا يَزِيدُ بْنُ هَارُونَ ، عَنْ يَحْيَى ، عَنْ مُوسَى بْنِ عُقْبَةَ ، عَنْ كُرَيْبٍ ، مَوْلَى ابْنِ عَبَّاسٍ عَنْ أُسَامَةَ بْنِ زَيْدٍ ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم لَمَّا أَفَاضَ مِنْ عَرَفَةَ عَدَلَ إِلَى الشِّعْبِ، فَقَضَى حَاجَتَهُ. قَالَ أُسَامَةُ بْنُ زَيْدٍ فَجَعَلْتُ أَصُبُّ عَلَيْهِ وَيَتَوَضَّأُ فَقُلْتُ يَا رَسُولَ اللَّهِ أَتُصَلِّي فَقَالَ " الْمُصَلَّى أَمَامَكَ " .
"When Allah's Messenger (ﷺ) departed from `Arafat, he turned towards a mountain pass where he answered the call of nature. (After he had finished) I poured water and he performed ablution and then I said to him, "O Allah's Messenger (ﷺ)! Will you offer the prayer?" He replied, "The Musalla (place of the prayer) is ahead of you (in Al-Muzdalifa).